How to get a refund for an accidental in app purchase from the App Store?

Please help me and sorry because my english, My little doughter bought subscription in one game and I lose 21.99$ today I need help to get the money back , Because a little kid did it and I didn't know , My doughter bought subscription in the game and it called “Ms Yvonne:face aging editor it cost

21.99$ when i saw this i did cancelled this subscription

[Edited by Moderator]